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 /*
	 File:       RTCPSRPacket.cpp

	 Contains:   A class that writes a RTCP Sender Report

	 Change History (most recent first):



 */

#include <string.h>

#include "RTCPSRPacket.h"
#include "MyAssert.h"
#include "OS.h"

RTCPSRPacket::RTCPSRPacket()
{
	// Write as much of the Sender Report as is possible
	char theTempCName[kMaxCNameLen];
	UInt32 cNameLen = RTCPSRPacket::GetACName(theTempCName);

	//write the SR & SDES headers
	UInt32* theSRWriter = (UInt32*)&fSenderReportBuffer;
	*theSRWriter = htonl(0x80c80006);
	theSRWriter += 7; //number of UInt32s in an SR.

	//SDES length is the length of the CName, plus 2 32bit words, plus the 32bit word for the SSRC
	*theSRWriter = htonl(0x81ca0000 + (cNameLen >> 2) + 1);
	::memcpy(&fSenderReportBuffer[kSenderReportSizeInBytes], theTempCName, cNameLen);
	fSenderReportSize = kSenderReportSizeInBytes + cNameLen;

	/*
	 SERVER INFO PACKET FORMAT
	struct qtss_rtcp_struct
	{
		RTCPHeader      header;
		UInt32          ssrc;       // ssrc of rtcp originator
		OSType          name;
		UInt32          senderSSRC;
		SInt16          reserved;
		SInt16          length;     // bytes of data (atoms) / 4
		// qtsi_rtcp_atom structures follow
	};
	*/

	//
	// Write the SERVER INFO APP packet
	UInt32* theAckInfoWriter = (UInt32*)&fSenderReportBuffer[fSenderReportSize];
	*theAckInfoWriter = htonl(0x81cc0006);
	theAckInfoWriter += 2;
	*(theAckInfoWriter++) = htonl(FOUR_CHARS_TO_INT('q', 't', 's', 'i')); // Ack Info APP name
	theAckInfoWriter++; // leave space for the ssrc (again)
	*(theAckInfoWriter++) = htonl(2); // 2 UInt32s for the 'at' field
	*(theAckInfoWriter++) = htonl(FOUR_CHARS_TO_INT('a', 't', 0, 4));
	fSenderReportWithServerInfoSize = (char*)(theAckInfoWriter + 1) - fSenderReportBuffer;

	UInt32* theByeWriter = (UInt32*)&fSenderReportBuffer[fSenderReportWithServerInfoSize];
	*theByeWriter = htonl(0x81cb0001);
}

UInt32 RTCPSRPacket::GetACName(char* ioCNameBuffer)
{
	static char*    sCNameBase = "QTSS";

	//clear out the whole buffer
	::memset(ioCNameBuffer, 0, kMaxCNameLen);

	//cName identifier
	ioCNameBuffer[0] = 1;

	//Unique cname is constructed from the base name and the current time
	qtss_sprintf(&ioCNameBuffer[1], " %s%" _64BITARG_ "d", sCNameBase, OS::Milliseconds() / 1000);
	UInt32 cNameLen = ::strlen(ioCNameBuffer);
	//2nd byte of CName should be length
	ioCNameBuffer[1] = (UInt8)(cNameLen - 2);//don't count indicator or length byte

	// This function assumes that the cName is the only item in this SDES chunk
	// (see RTP rfc for details).
	// The RFC says that the item (the cName) should not be NULL terminated, but
	// the chunk *must* be NULL terminated. And padded to a 32-bit boundary.
	//
	// qtss_sprintf already put a NULL terminator in the cName buffer. So all we have to
	// do is pad out to the boundary.
	cNameLen += 1; //add on the NULL character
	UInt32 paddedLength = cNameLen + (4 - (cNameLen % 4));

	// Pad, and zero out as we pad.
	for (; cNameLen < paddedLength; cNameLen++)
		ioCNameBuffer[cNameLen] = '\0';

	Assert((cNameLen % 4) == 0);
	return cNameLen;
}
